Newer generation transcatheter aortic valve prostheses are designed to overcome the limitations of early-generation devices that were susceptible to malpositioning, paravalvular aortic regurgitation, atrioventricular (AV)-conduction disturbances and vascular complications. In this issue of JACC: Cardiovascular Interventions, Rampat et al. (1) report the UK experience with the novel repositionable LOTUS prosthesis (Boston Scientific, Natick, Massachusetts) in 228 patients enrolled at 10 sites. The LOTUS valve system is a newer generation transcatheter aortic valve prosthesis made of a single nitinol wire that is braided into a stent frame of 19-mm height housing a trileaflet bovine pericardial valve. After positioning of the stent frame, which is guided by a tantalum marker, the prosthesis is locked in its final configuration. The valve prosthesis comes pre-mounted on a delivery catheter and accommodates an annulus diameter ranging from 20 to 27 mm with currently 3 prosthesis sizes (23, 25, and 27 mm). The full repositionability of the LOTUS valve allows for careful assessment of the result after deployment in its final configuration before release. Pre-implantation balloon valvuloplasty is not obligatory, and the device can be deployed without rapid ventricular pacing. In a high-risk patient population with both aortic stenosis and aortic regurgitation, the periprocedural success rate was 99% via the transfemoral or transaortic route and was paralleled by a low in-hospital mortality rate of 1.8%. Of note, moderate or severe paravalvular aortic regurgitation was strikingly low at 0.8%. In turn, almost 1 in every 3 patients required implantation of a permanent pacemaker after the procedure.

Adverse events related to transcatheter aortic valve replacement (TAVR) can be categorized according to severity and timing of their occurrence. Improved patient selection, multimodal imaging techniques, and a team-oriented approach have contributed to reducing the rate of technical complications encountered with early-generation devices and form a robust basis for the refinement of subsequent iterations of TAVR devices.

Access-related complications and bleeding remain the single most common periprocedural complications associated with increased mortality and have primarily been addressed by reducing the profile of delivery catheters. Vascular access–related complications amounted to 7% in the present registry, in line with comparable cohorts from the UK TAVI registry and GARY (German Aortic Valve Registry) (1,2). The Boston Scientific LOTUS prosthesis uses an 18- to 20-F delivery catheter system, comparable to the St. Jude Medical (St. Paul, Minnesota) PORTICO, the Symetis SA (Ecublens, Switzerland) ACURATE, and the DirectFlow Medical (Santa Rosa, California) devices. Although it is expected that future iterations of the LOTUS prosthesis will result in further downsizing of the delivery catheter, the currently available Edwards SAPIEN 3 (Edwards Lifesciences, Irvine, California) and the Medtronic (Minneapolis, Minnesota) EVOLUT R transcatheter valves use smaller delivery sheaths (14- to 16-F) and enable transfemoral TAVR in even more challenging peripheral anatomies, increasing the adoption of a predominantly transfemoral access site in >90% of cases today.

Cerebrovascular events remain the most devastating periprocedural complication. The risk of periprocedural stroke is determined by a combination of inherent patient- and procedure-related characteristics as well as pharmacotherapy and ranges from 1.5% to 4% in recent registries (2–4). Consistently, the stroke rate was 3.9% in the UK LOTUS registry (1). Lower profile, flexible, pre-curved, and steerable delivery catheters designed to negotiate the prosthesis across the aortic arch intuitively mitigate the risk of plaque abrasion. Repeated attempts to properly position the transcatheter valve prosthesis within the aortic annulus has been correlated with an increased risk of stroke with early-generation devices. It remains to be determined whether the obvious appeal of a fully repositionable transcatheter heart valve is undermined by repeated attempts to reposition the device.

The extension of TAVR to lower risk patient populations entails a shift in focus from periprocedural device success to long-term effectiveness and subjects newer generation TAVR prostheses to more intense scrutiny. Paravalvular aortic regurgitation, structural valve deterioration, and atrioventricular (AV) conductance disturbances increasingly enter the limelight as important determinants of long-term prognosis. Moderate and severe paravalvular aortic regurgitation have consistently been associated with impaired long-term outcomes (3,5). Early-generation devices exhibited mild aortic regurgitation in more than half of the patients (5) and moderate or severe aortic regurgitation in 3% to 14% of patients (3,5). Efforts to mitigate aortic regurgitation include imaging tools to facilitate precise device positioning, repositionable devices, internal skirts, and external cuffs sealing the prosthesis to the aortic annulus. In the UK LOTUS registry, the incidence of moderate or severe aortic regurgitation was only 0.8%, and more than three-fourths of all patients had no aortic regurgitation at all (1). These findings that are consistent with the REPRISE II (Repositionable Percutaneous Replacement of Stenotic Aortic Valve Through Implantation of Lotus Valve System: Evaluation of Safety and Performance) registry provide surgery-like outcomes and are an important prerequisite to allow extension of TAVR to lower risk patients (6). A low incidence of relevant paravalvular aortic regurgitation has also been observed with the Edwards SAPIEN 3 prosthesis, which was shown to reduce the risk of paravalvular regurgitation compared with the Edwards SAPIEN XT valve (1.3% vs. 5.3%, p = 0.04) (7), and the Medtronic EVOLUT R prosthesis was reported to have moderate paravalvular aortic regurgitation in 3.4% of patients in the CE Mark Clinical Study (8). The full repositionability of the LOTUS device allowing for optimization of the results before release may further contribute to the very low rate of paravalvular aortic regurgitation, and outcomes of randomized clinical trials will reveal relevant differences between devices. Improved placement, better conformability, and lower rates of paravalvular regurgitation with the newer generation transcatheter valves may result in lesser degrees of valve deterioration.

Consistent with the REPRISE II study (6), the rate of AV conductance disturbances was relatively high, and permanent pacemaker implantation was needed in 31.8% of the present registry (1). The impact of permanent pacemaker implantation on long-term outcome remains controversial. In a prospective registry of 353 patients from 2 institutions, no difference in mortality was observed between patients with a previously implanted permanent pacemaker, a newly implanted permanent pacemaker, or no pacemaker, respectively, at 1 year (9). In contrast, new permanent pacemaker implantation was an independent predictor of mortality in a subanalysis of the PARTNER (Placement of AoRTic TraNscathetER Valve) trial (hazard ratio: 1.38, 95% confidence interval: 1.00 to 1.89; p = 0.05) (10), in which the Edwards SAPIEN XT prosthesis was exclusively used. Ventricular dyssynchrony resulting from chronic right ventricular pacing may account for an adverse long-term prognosis in patients with a high degree of pacemaker dependency. However, AV conductance disturbances after TAVR may only be transient. Moreover, as many as 1 in 4 patients qualifying for TAVR according to current guidelines already had a permanent pacemaker before the procedure (10). The issue of permanent pacemaker implantation will certainly be more relevant in lower risk, younger patients, and future studies will need to carefully evaluate the long-term sequelae of permanent pacemaker dependence.

In summary, the article by Rampat et al. reports the largest experience to date with the fully repositionable LOTUS valve system and highlights several features that represent a valuable asset in the treatment of patients with valvular heart disease. The device can be implanted without systematic pre-dilation and obviates the need for rapid ventricular pacing, which may be helpful in the treatment of patients with severely compromised left ventricular function. It also allows for reliable assessment and reversibility of coronary obstruction in case of close proximity of the coronary ostia to the aortic valve annulus and enables easy access to the coronary tree after valve deployment in view of the limited height of the valve frame. Most importantly, paravalvular regurgitation can be assessed and corrected before valve release, resulting in rates of residual paravalvular aortic regurgitation that are exceedingly low and comparable to surgical aortic valve replacement. Off-label use of the device in patients with degenerated bioprosthetic valves and transaortic access will further increase the applicability of the prosthesis. Initial experience from isolated cased of transapical implantation of the LOTUS prosthesis during mitral valve-in-ring interventions also takes advantage of the repositionable feature to assess left ventricular outflow tract obstruction before release. Promising safety outcomes in the short term will need to be supported by continued effectiveness data during extended follow-up. Refinement of the system with smaller delivery catheter profiles and extension of the device range to accommodate larger aortic valve anatomies will further increase the use of this newer generation transcatheter prosthesis.

Footnotes

↵∗ Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.

Dr. Pilgrim has received speaker fees from Biotronik and Medtronic. Dr. Windecker has received institutional research grants from Abbott, Biotronik, Boston Scientific, Edwards Lifesciences, Medtronic, The Medicines Company, and St. Jude Medical.